Carreno Busta was pushed all the way by Albert Ramos-Vinolas in a pulsating semi-final, ultimately coming through 6-1 3-6 7-6 (7-5).
"It was so close. I don't know what happened in the second set," Carreno said. "At the beginning of the match, I was very focussed on my game and being aggressive.
"After that, Albert, of course, started to push [back] more and [I] started to lose my level a little bit.
"I just kept fighting all the time, and I want to thank everyone [in the crowd] for their support. This is what we missed last year, the crowd. It's very important to play these kinds of very close matches with a crowd like this."
He will take on Munar after the 23-year-old edged past Carlos Alcaraz 7-6 (7-4) 6-4.
Munar, who reached a final on the ATP Challenger Tour last week, said: "I feel happy and excited. I've been working a lot during the last [few] months.
"It's a gift for me to be here in a final, and especially in Marbella which is one of my favourite places. I feel excited."
Elsewhere, Lorenzo Sonego is aiming to become the first Italian to win an ATP Tour clay-court title on home soil for 15 years when he takes on Laslo Djere in the final of the Sardegna Open on Sunday.
Sonego, 25, overcame American Taylor Fritz 6-4 5-7 6-1 to give himself the opportunity to add to his Antalya Open title from 2019.
Standing in his way is Serbian Djere, who cruised past Nikoloz Basilashvili 6-2 6-0 in just 52 minutes.
Djere was in control from the outset and from 3-2 in the first set went on to win nine straight games, helping him to his third ATP Tour final.
Hunting a fifth Tour title, top-seed Carreno Busta needed three sets to overcome compatriot Jaume Munar 6-1 2-6 6-4 in Marbella.
It is his 200th tour-level win, though it took him two hours and 21 minutes to claim his maiden Spanish title, and his first win since 2019.
Carreno Busta certainly had to work hard for it, with Munar having battled to 4-4 in the decider.
Yet a seventh break point of the ninth game was taken by Carreno Busta, whose powerful backhand return forced his 23-year-old opponent into an error.
Meanwhile, Sonego became the first Italian since Filippo Volandri in October 2006 to win an ATP Tour title on home soil as he overcame Laslo Djere in the Sardegna Open.
Serbian Djere was on a nine-match winning streak in Italy, but Sonego – who won the doubles title on Saturday – succeeded 2-6 7-6 (7-5) 6-4.
Sonego is the first player since Feliciano Lopez at the 2019 Queen's Club Championships to win both the doubles and singles titles, and the first Italian to do so since Matteo Berrettini at the 2018 Swiss Open Gstaad.
It represents a second tour-level triumph for world number 34 Sonego, who previously won the 2019 Antalya Open.
Carreno Busta demolished seventh seed Soonwoo Kwon 6-4 6-0, while Casper Ruud was stunned in straight sets by wildcard Alcaraz.
The 17-year-old backed up his victory over the veteran Feliciano Lopez in style, becoming the youngest ATP Tour semi-finalist since Alexander Zverev at Hamburg in 2014 with a 6-2 6-4 win.
Albert Ramos-Vinolas will face Carreno Busta after beating Norbert Gombos 6-7 (4-7) 7-5 6-4, while Alcarez is next on the agenda for compatriot Jaume Munar, who was taken the distance by Ilya Ivashka having overcome second seed Fabio Fognini on Thursday.
Taylor Fritz continued his solid form this season with a straight sets victory over Aljaz Bedene to reach the semi-finals of Sardegna Open.
Fritz is playing as the US number one for the first time in Cagliari this week and he made light work of Bedene, prevailing 6-3 6-4 to book a showdown with third seed Lorenzo Sonego, who beat Yannick Hanfmann 3-6 7-6 (8-6) 6-3 despite being 3-5 down in the second.
Seeded second and ranked 30 in the world, Fitz improved his 2021 record to 11-5 and will look to avenge a defeat in his only other meeting with Sonego on clay, when he lost at Roland Garros last year.
Lorenzo Musetti thrilled as he saved four match points to sink top seed Dan Evans on Thursday but bowed out after another epic, losing to Serbia's Laslo Djere 6-4 4-6 6-2 in two hours and 21 minutes.
Djere, who beat sixth seen John Millman en route to the quarter-finals, will face Nikoloz Basilashvili after the battle between seeds four and five ended 7-5 4-6 6-3 in the Georgian's favour.
The 2016 champion, Carreno Busta had his sights set on the semi-finals of the ATP 250 tournament but he suffered a surprise 7-6 (7-2) 6-3 loss on Thursday.
"Of course it's a great feeling. I had a great match today. These conditions suit me," Ivashka said. "I think he had more pressure because he's the top seed so for me it was a good challenge to see what my level is and to compete with these guys, so for me it was a great match."
Carreno Busta – who trumped world number one and 20-time grand slam champion Novak Djokovic to win bronze at the Olympic Games – was not the only seed to fall.
Richard Gasquet and Frances Tiafoe also crashed out in the quarter-finals following defeats to Emil Ruusuvuori and Mikael Ymer.
The only seed to advance to the semis was 15th seed Carlos Alcaraz, who saw off Marcos Giron.
Carreno Busta – the 2016 champion – was too good for Dominik Koepfer 6-2 6-3 at the ATP 250 tournament on Wednesday.
The Spaniard, who stunned world number one Novak Djokovic to win bronze at the Olympic Games, will meet Ilya Ivashka, who upstaged ninth seed Jan-Lennard Struff 6-2 6-1.
"It was a very good match. I think I played very aggressively today, I made a lot of winners," Carreno Busta said. "I played against him the last two tournaments so it was important to me at the beginning of the match to be very focused and play very aggressive so I think this was a very good match for me.
"I'm feeling really comfortable playing this year, also. We know next we have the US Open but day by day I need the confidence, I need the rhythm. I think that I'm playing at a really good level so I would like to continue this way."
Former world number seven Richard Gasquet saw off third seed Daniel Evans 6-4 7-6 (7-4), Frances Tiafoe defeated Thiago Monteiro 7-5 7-6 (7-2), while fourth seed Marton Fucsovics was sent packing by Carlos Alcaraz 6-3 0-6 6-2.
Cerundolo had lost his only previous final, again against a fellow countryman in the form of Diego Schwartzman at last year's Argentina Open.
But he was not to be denied this time around on the clay in Bastad on Sunday.
The two players went into this tournament with just five places separating them in the ATP rankings, and they proved to evenly matched in the first set.
World number 34 Baez struck with a break in the opening game only for the 39-ranked Cerundolo to immediately hit back in kind.
Cerundolo saved six break points to hold for a 6-5 lead but then saw two set points go begging.
He dominated the subsequent tie-break, however, and maintained the momentum in the second, serving out a 7-6 (7-4) 6-2 win to love.
Coria came from a set down to win 4-6 6-2 6-0 in the first-round match in the Serbia Open against ATP Tour debutant Marko Topo.
Chardy overcame Tennys Sandgren 6-4 6-2. The Frenchman started the season well, and managed two semi-final runs, but has been out of form in recent competitions and was knocked out in the first round at the Madrid Masters earlier this month.
Meanwhile, Pedja Krstin made home advantage count against Kwon Soonwoo.
The trio will be joined in the second round by top seed and world number one Novak Djokovic, who received a first-round bye and is in the hunt for his third title in Belgrade.
At the Parma Open, American Tommy Paul reeled off a 7-5 6-4 win over Stefano Travaglia, and Flavio Cobolli beat Marcos Giron 3-6 7-6 (8-6) 7-6 (7-4).
Chardy saved six set points before being taken do a decider by Barrere, who passed up six chances to break his opponent and succumbed to a 6-3 3-6 6-3 defeat.
Seventh seed Adrian Mannarino exited after a 6-3 6-4 loss to Alexander Bublik, while Filip Krajinovic – seeded sixth – came from a set down to beat Kyle Edmund 4-6 6-3 6-3.
There were also wins for Fernando Verdasco, Aljaz Bedene, Corentin Moutet and Miomir Kecmanovic.
The grass-court swing got under way with four main-draw matches but little drama in Germany.
One-time Wimbledon finalist Cilic staved off the only two break points he faced against wildcard Rudolf Molleker and seized all five opportunities of his own.
A 7-5 6-3 win was enough to set up a second-round meeting with fifth seed Nikoloz Basilashvili, who beat Dustin Brown in the top half of the draw.
The defeated pair were the only home hopefuls in action, while number six seed Ugo Humbert and Lloyd Harris each also progressed.
Rinderknech, who sits 65th in the world rankings, had not recorded a Tour-level victory before 2021 but has now triumphed 15 times after cruising past Delbonis 6-4 6-4.
The Frenchman will meet eighth seed Dusan Lajovic in the second round in Antwerp, after the Serbian downed Richard Gasquet 7-6 (7-3) 6-1 on Monday.
The other first-round clash in Belgium saw Alexei Popyrin capitulate in the third set as he succumbed to a 4-6 6-3 0-6 defeat against world number 62 Botic van de Zandschulp.
Americans Jenson Brooksby and Brandon Nakashima also booked their places in the main draw. Brooksby defeated Norbert Gombos 6-4 6-2, while Nakashima overcame Pierre-Hugues Herbert 6-2 6-4.
Meanwhile in Russia, Cilic – who has claimed the crown in Moscow twice previously – recovered from a first-set scare in his round-of-32 tie with qualifier Damir Dzumhur, eventually triumphing 6-7 (4-7) 6-1 6-1.
John Millman experienced similar difficulties, with Benjamin Bonzi claiming the first set before the Australian succeeded 6-7 (5-7) 6-4 6-3 to set up a potential second-round match against fifth seed Alexander Bublik.
The former world number three beat Taro Daniel 7-5 6-4 on Wednesday, winning 82 per cent of his first-serve points in an encouraging performance as he attempts to win a ninth indoor Tour title.
Should Cilic lift the trophy, he would join Roger Federer (103), Rafael Nadal (86), Novak Djokovic (82), Andy Murray (46) and Juan Martin del Potro (22) as the only active male players to win at least 20 Tour-level titles.
"It is the beginning of the season and my third match of the year, so I am still feeling a little bit rusty," said Cilic. "Overall, it was a solid match. [It is] something I definitely needed for the start of the tournament."
The Croatian will face Kwon Soon-woo in the quarter-finals, while Yoshihito Nishioka and Alexander Bublik were among the others to progress.
Jannik Sinner was a surprise casualty at the Open Sud de France, the world number 34 losing in three sets to Aljaz Bedene in a match that lasted nearly two hours and 40 minutes.
Sixth seed Ugo Humbert battled past Dutch qualifier Tallon Griekspoor in a match with three tie-breaks, while second seed David Goffin went the distance to overcome wildcard Benjamin Bonzi 4-6 6-4 7-5.
A decade on from lifting the trophy for the first time, Cilic outlasted his American opponent 7-6 (7-3) 4-6 6-4 in a gruelling contest lasting two hours and 23 minutes.
It took the Croatian to four tournament wins on Russian soil, the 33-year-old having also twice won the crown in Moscow, while it also saw him join truly elite company in the men's game.
Only five other active male players have won 20 or more titles: Roger Federer (103), Rafael Nadal (88), Novak Djokovic (85), Andy Murray (46) and Juan Martin del Potro (22).
"Coming 10 years after winning in 2011 and also winning now, it's so, so special for me, especially this part of my career," said Cilic. "Having now a family, two sons, I want to absolutely dedicate this trophy to my newborn son."
Cilic had the chance to reach 20 titles last week in Moscow, only to lose in straight sets to home favourite Aslan Karatsev.
With 12 aces and 78 per cent of first-serve points won, the former world number three was aggressive in his efforts to make sure this was not another missed opportunity.
After taking the first set, Cilic twice led by a break in the second but allowed Fritz to level the contest and keep alive his hopes of a first title since Eastbourne two years ago.
Fritz went a break ahead in the decider but Cilic battled back to level at 4-4. A double fault from the world number 28 gave Cilic the chance to serve out the contest, and he duly obliged, converting his first match point with a volley.
The former world number three is aiming to become the sixth active player to reach 20 titles on the ATP Tour this week but was staring down the barrel when trailing 5-4 in the deciding set.
But Cilic survived to record a 6-2 2-6 7-5 win against his Korean opponent and earn a last-four date with Alexei Popyrin, following the Australian's straight-sets win over compatriot Matthew Ebden.
"I think that the third set was solid from the both of us, it was a great match and it went to the end," Cilic said. "At 5-5 [in the third set], I kept my focus and felt that I was going to get my chance.
"There were a few break opportunities that I couldn't convert, but on the third one, I hit a great return."
Radu Albot is into a first ATP Tour semi-final in 19 months after knocking out top seed Adrian Mannarino 6-3 6-4. His reward is a semi-final with Alexander Bublik, who overcame fifth seed Yoshihito Nishioka in straight sets.
At the Open Sud de France, top seed Roberto Bautista Agut made short work of Ugo Humbert in a 6-3 6-3 win. He next faces Peter Gojowczyk after the German routed Dennis Novak 6-4 6-1.
Second seed David Goffin cruised past Lorenzo Sonego 6-4 6-4 and will play Egor Gerasimov in the last four after his three-sets win over Alejandro Davidovich Fokina.
This has been a tough season for the Australian, who had not managed to wins at the same Tour-level event since the Australian Open until this week.
But a string of impressive results against Fernando Verdasco, Tommy Paul and then Frances Tiafoe secured a final meeting with Mannarino.
The Frenchman's 2020 struggles have been even more stark, taking a 6-14 record to Kazakhstan, and he proved an accommodating opponent for Millman, failing to take his opportunities.
Five break points came and went for Mannarino in the first set before Millman broke at the first attempt to take the opener.
Mannarino then offered little resistance in the second, waiting until the final game to squander his sixth and last chance as Millman claimed a straight-sets win.
Federico Coria, seeded sixth, overcame reigning champion and 2021 runner-up Albert Ramos-Vinolas 6-4 7-6 (7-2) after over two-and-a-half hours of action.
The world number 67, who is into his second ATP Tour-level final and is set to rise into the top 50 of the rankings, has dropped just a single set in the tournament.
Sebastian Baez, eight years Coria's junior, is aiming for his second title after winning in Estoril last year.
The 22-year-old fourth seed defeated Hugo Dellien 6-4 6-4.
This will be the fourth singles final of Baez's career, though his first on home soil.
"It means a lot, but [it brings] confidence," said Baez.
"I have my people here, my friends, my family, everything, so that is a big motivation for me."
While Coria and Baez have just five previous final appearances between them, John Isner advanced to a 31st Tour-level showdown of his career as he beat fellow American J.J. Wolff at the Dallas Open.
Playing in his home city, 37-year-old Isner came from behind to prevail 3-6 7-5 7-6 (7-4).
Isner offered up eight break points, but saved seven of them to frustrate Wolff.
"I saved a lot of break points with unreturnable serves," Isner said. "Without that I would have been dusted off the court 6-3, 6-4. I'm of course very fortunate to have that weapon in my pocket, and I needed every bit of it today.
"It was an absolute battle, so I'm pretty tired. But I'm absolutely ecstatic to be in the final tomorrow here in Dallas."
Asked how he was faring up after his long tussle with Wolff, Isner quipped: "Truthfully, it feels terrible right now. I'm 38 in April. It's not getting any easier. I started off a little slow, a little sluggish, but in the third set I actually felt the best I felt the whole match.
"I had a lot of adrenaline there at the end and I was able to hold my nerve and win. Right now the name of the game is recovery."
Isner will be the favourite in the final, after top seed Fritz surrendered a lead in a 6-7 (3-7) 7-5 6-4 loss to Wu Yibing.
Paris-born American Cressy won 7-5 6-7 (3-7) 7-6 (7-4) in a little over two and a half hours, countering 10 double faults with 15 aces on his way to victory.
Rune, the Danish 19-year-old who sits ninth in the world rankings, had won his three previous matches against Cressy, including a second-round clash at the Australian Open last month, but he could not extend that dominance at the indoor event in Montpellier.
It means Cressy faces second seed Sinner, a player he lost to at a low-level tournament in Lexington in 2019, their only past meeting.
Sinner beat 18-year-old French wildcard Arthur Fils in Saturday's first semi-final, ending the teenager's eye-catching run with a 7-5 6-2 victory.
Fils had beaten Richard Gasquet and Roberto Bautista Agut on his way to the last four but found world number 17 Sinner was more than his match.
Last year saw Sinner reach just one ATP final, taking a title on clay in Umag, after making it through to five title matches in the 2021 season.
He had his best year at the grand slams, however, reaching quarter-finals at three of the four majors.
Cressy recognises the threat posed by the Italian, saying in an on-court interview: "Jannik Sinner is an incredible player, just like Holger Rune and everyone else in the tournament. I believe you've just got to bring your 'A' game every time and I'm really looking forward to it."
Competing well in France has been pleasing for Cressy, who is set to climb from 51st in the rankings and into the top 40 on Monday.
"I lived and grew up here, and I'm extremely happy," Cressy said.
Cressy will play his third championship match of the year on Sunday following a 6-2 4-6 6-3 defeat of his fellow American in Newport.
The 25-year-old fired down 22 aces and won 82 per cent of points behind his first serve, breaking three times to move into the final.
Cressy had a stroke of luck for the only break of the deciding set, when he lobbed a shot just over the net and it bounced back onto his side to leave Isner 5-3 down. He then served out the match to end Isner's 10-match winning run in this event.
Bublik sealed his place in the final with a 6-3 6-2 victory over Jason Kubler.
Third seed Bublik did not face a break point and broke the Australian three times, sealing his victory in an hour and nine minutes.
There will be an all-Argentinian final at the Swedish Open between Francisco Cerundolo and Sebastian Baez.
Baez produced an upset, securing his first win against a top-10 opponent with a 6-2 6-4 defeat of second seed Andrey Rublev in Bastad.
Cerundolo got the better of Pablo Carreno Busta 6-3 6-2, ensuring he will face his compatriot for the first time at tour-level.
De Minaur lost the first set against his Italian opponent, who reached a career-high ranking of 26 earlier this month, but the Australian fought back to prevail 4-6 6-4 7-6 (7-5).
Having forced a decider, it was De Minaur who had the most left in the third-set tie-break, which decided an entertaining contest that lasted two hours and 40 minutes.
It marked De Minaur's second title of 2021 following his success at the Antalya Open back in January.
Prior to Saturday, all four of De Minaur's ATP titles had come on hard courts.
However, an excellent backhand return of a second serve set him up for a forehand smash to clinch a triumph that should give him great confidence heading into Wimbledon.
De Minaur starts his campaign at the All England Club on Monday with a testing opening clash against Sebastian Korda while Sonego faces Pedro Sousa.
Speaking at the presentation, De Minaur paid tribute to Sonego, who recently lost his grandmother.
"Everyone should congratulate Lorenzo for an incredible week. Everyone should be scared of you at Wimbledon next week," said De Minaur.
"It's been a long week, I've played some great tennis, I've managed to pull through a very tough win.
"Hopefully I can keep it going through Wimbledon, I can't wait to go there next week."
It was a tremendous week in Acapulco for the Australian, having eliminated world number 10 Holger Rune in the semi-final en route to his seventh title overall, with the first six all at the ATP 250 level.
Against Paul, De Minaur blew a pair of break points in the opening set, and then gave up the break in the very next game, allowing the American to serve things out safely to take the first frame.
But mistakes started to creep into Paul's game the longer the match went. After landing 75 per cent of his first serves fair in the opener and avoiding any double-faults, Paul's first serve percentage dropped to 46 in the second, and he committed a pair of doubles.
He committed another two double-faults in the decider to hand De Minaur the early break, and his play from the baseline also deteriorated, hitting just six winners to go with 14 unforced errors.
Known for his resilience, De Minaur had to save five break points to hold serve in the opening game of the third set, but he held his nerve, and churned out five consecutive games as Paul ran out of gas.
The 500 ranking points will see the Aussie climb to 18th in the world, with his career-best mark of 15th now within reach.
Meanwhile, the fairytale continued for Nicolas Jarry at the Chile Open, with the Santiago-born talent electrifying his home crowd with a 1-6 7-6 (7-4) 6-1 semi-final victory over Jaume Munar.
Jarry will get a chance for the second ATP title of his career, and the first since 2019, when he meets Tomas Martin Etcheverry in the final.
Etcheverry emerged victorious 7-5 6-3 in an all-Argentine showdown against third seed Sebastian Baez, earning his first final appearance at this level.
It was a tremendous week in Acapulco for the Australian, having eliminated world number 10 Holger Rune in the semi-final en route to his seventh title overall, with the first six all at the ATP 250 level.
Against Paul, De Minaur blew a pair of break points in the opening set, and then gave up the break in the very next game, allowing the American to serve things out safely to take the first frame.
But mistakes started to creep into Paul's game the longer the match went. After landing 75 per cent of his first serves fair in the opener and avoiding any double-faults, Paul's first serve percentage dropped to 46 in the second, and he committed a pair of doubles.
He committed another two double-faults in the decider to hand De Minaur the early break, and his play from the baseline also deteriorated, hitting just six winners to go with 14 unforced errors.
Known for his resilience, De Minaur had to save five break points to hold serve in the opening game of the third set, but he held his nerve, and churned out five consecutive games as Paul ran out of gas.
The 500 ranking points will see the Aussie climb to 18th in the world, with his career-best mark of 15th now within reach.
Meanwhile, the fairytale continued for Nicolas Jarry at the Chile Open, with the Santiago-born talent electrifying his home crowd with a 1-6 7-6 (7-4) 6-1 semi-final victory over Jaume Munar.
Jarry will get a chance for the second ATP title of his career, and the first since 2019, when he meets Tomas Martin Etcheverry in the final.
Etcheverry emerged victorious 7-5 6-3 in an all-Argentine showdown against third seed Sebastian Baez, earning his first final appearance at this level.